The field of the invention is optical waveguide cables.
Optical waveguide cables have included powders therein designed to perform various functions such as absorbing or blocking water and inhibiting the propagation of flames or toxic smoke along a cable. The prior art discloses a number of methods to place such powders into cables. Arendt, et al., U.S. Pat. No. 3,538,235, discloses placing of a powder in a suspension in a highly volatile liquid forced into a cable under pressure. The powder mixture contains a 2% bonding agent such as polyisobutylene. Several prior art disclosures teach simply mixing the powder with plastic pellets in order that the powder be generally mixed in the plastic article to be extruded from the pellets; such is disclosed by Ogasawara et al., U.S. Pat. No. 4,767,184; and Anelli et al, U.S. Pat. No. 4,725,122. Hope, U.S. Pat. No. 4,401,366, discloses the application of powder with the aid of an electrostatic field. Other prior art patents, such as Anelli et al., U.S. Pat. No. 4,725,122, and Elion, U.S. Pat. No. 4,525,026, disclose the use of adhesives. Rawlyk, U.S. Pat. No. 5,039,197, discloses the use of heat curing.
It is believed that, for many cables, the most efficient use of powder in a plastic structure is to embed the powder only in the outer surface of the plastic article. The prior art has normally used adhesives to accomplish this purpose. Therefore, it is believed that the art would be advanced by cables and methods for making such cables involving the embedding of powders only in the outer surface of plastic articles and without having to deal with adhesives.